Reinstalling the launcher should be as easy as uninstalling and installing again, but there are some caveats.
The launcher files are pretty small in size and should hopefully not take too long to download. However, when uninstalling the launcher, it's possible that the game files, which are contained in the SharedCache folder, will also be removed.
To prevent having to download the whole game again when we just want to download the launcher, see the steps below:
Get the latest launcher
Download the latest launcher from the main download page:
https://community.eveonline.com/support/download
Check the SharedCache folder
Look in the installation folder
\Eve Online\
Open the SharedCache folder
- If the SharedCache folder is empty then it's possible that the game files are located in another location on your hard drive, which means that uninstalling the launcher will not affect the folder.
- If the SharedCache folder is not empty, then you will want to move this folder to another location in your computer manually, as uninstalling the launcher will also remove the SharedCache files.
Uninstall
To uninstall the launcher, go to Control Panel then open the “Programs and Features” section. There, find EVE Online and press Uninstall. Verify that the program directory matches with the installation folder you were looking at earlier.
Don't worry, your client settings will not be wiped by this operation.
Reinstall
Run the EveLauncher.exe that you downloaded in the first step. After you've clicked Next a few times it gets to the actual installation phase, you will get a dialog asking you to run the launcher. Answer "No" to ensure the shared cache will be stored wherever you installed the launcher this time.
On the final dialog, be sure to uncheck the “Run EVE Online now” checkbox.
Restore the shared cache
Open your installation folder again and move the SharedCache folder you set aside earlier to replace the now empty SharedCache folder.
Start the launcher
Now you should be able to run the launcher again, with all downloaded files intact.